Card-O-Rama: Magnetic Stripe Technology and Beyond
or
"A Day in the Life of a Flux Reversal"
Written by
oooOO Count Zero OOooo
Restricted Data Transmissions
November 22, 1992
Look in your wallet. Chances are you own at least 3 cards that have magnetic
stripes on the back. ATM cards, credit cards, calling cards, frequent flyer
cards, ID cards, passcards,...cards, cards, cards! And chances are you have NO
idea what information is on those stripes or how they are encoded. This
detailed document will enlighten you and hopefully spark your interest in this
fascinating field. None of this info is "illegal"...but MANY organizations
(the government, credit card companies, security firms, etc.) would rather keep
you in the dark. Also, many people will IMMEDIATELY assume that you are a
CRIMINAL if you merely "mention" that you are "interested in how magnetic
stripe cards work." Watch yourself, ok? Just remember that there is nothing
wrong with wanting to know how things work, although in our present society,
you may be labelled a "deviant" (or worse, a "hacker")!
Anyway, I will explain in detail how magstripes are encoded and give several
examples of the data found on some common cards. I will also cover the
technical theory behind magnetic encoding, and discuss magnetic encoding
alternatives to magstripes (Wiegand, barium ferrite). Non-magnetic card
technology (bar code, infrared, etc.) will be described. Finally, there will
be an end discussion on security systems and the ramifications of emergent
"smartcard" and biometric technologies.
*DISCLAIMER*
Use this info to EXPLORE, not to EXPLOIT. This text is presented for
informational purposes only, and I cannot be held responsible for anything you
do or any consequences thereof. I do not condone fraud, larceny, or any other
criminal activities.
*A WARNING*
Lately, I've noticed a few "books" and "magazines" for sale that were FILLED
with FILES on a variety of computer topics. These file were originally
released into the Net with the intention of distributing them for FREE.
HOWEVER, these files are now being PACKAGED and sold FOR PROFIT. This really
pisses me off. I am writing this to be SHARED for FREE, and I ask no payment.
Feel free to reprint this in hardcopy format and sell it if you must, but NO
PROFITS must be made. Not a fucking DIME! If ANYONE reprints this file and
tries to sell it FOR A PROFIT, I will hunt you down and make your life
miserable. How? Use your imagination. The reality will be worse.
** MAGSTRIPE FIELDS, HEADS, ENCODING/READING **
Now, I'll get down to business!
First, I am going to explain the basics behind fields, heads, encoding and
reading. Try and absorb the THEORY behind encoding/reading. This will help
you greatly if you ever decide to build your own encoder/reader from scratch
(more on that later). FERROMAGNETIC materials are substances that retain
magnetism after an external magnetizing field is removed. This principle is
the basis of ALL magnetic recording and playback. Magnetic POLES always occur
in pairs within magnetized material, and MAGNETIC FLUX lines emerge from the
NORTH pole and terminate at the SOUTH. The elemental parts of MAGSTRIPES are
ferromagnetic particles about 20 millionths of an inch long, each of which acts
like a tiny bar magnet. These particles are rigidly held together by a resin
binder. The magnetic particles are made by companies which make coloring
pigments for the paint industry, and are usually called pigments. When making
the magstripe media, the elemental magnetic particles are aligned with their
North-South axes parallel to the magnetic stripe by means of an external
magnetic fields while the binder hardens.
These particles are actually permanent bar magnets with TWO STABLE POLARITIES.
If a magnetic particle is placed in a strong external magnetic field of the
opposite polarity, it will FLIP its own polarity (North becomes South, South
becomes North). The external magnetic field strength required to produce this
flip is called the COERCIVE FORCE, or COERCIVITY of the particle. Magnetic
pigments are available in a variety of coercivities (more on that later on).
An unencoded magstripe is actually a series of North-South magnetic domains
(see Figure 1). The adjacent N-S fluxes merge, and the entire stripe acts as a
single bar magnet with North and South poles at its ends.
Figure 1: N-S.N-S.N-S.N-S.N-S.N-S.N-S.N-S N-----------------------------S
However, if a S-S interface is created somewhere on the stripe, the fluxes will
REPEL, and we get a concentration of flux lines around the S-S interface (same
with N-N interface). ENCODING consists of creating S-S and N-N interfaces, and
READING consists of (you guessed it) detecting 'em. The S-S and N-N interfaces
are called FLUX REVERSALS.
||| ||| ||| |||
The external magnetic field used to flip the polarities is produced by a
SOLENOID, which can REVERSE its polarity by reversing the direction of CURRENT.
An ENCODING head solenoid looks like a bar magnet bent into the shape of a ring
so that the North/South poles are very close and face each other across a tiny
gap. The field of the solenoid is concentrated across this gap, and when
elemental magnetic particles of the magstripe are exposed to this field, they
polarize to the OPPOSITE (unlike poles attract). Movement of the stripe past
the solenoid gap during which the polarity of the solenoid is REVERSED will
produce a SINGLE flux reversal (see Figure 3). To erase a magstripe, the
encoding head is held at a CONSTANT polarity and the ENTIRE stripe is moved
past it. No flux reversals, no data.
| | from NS to *SN*, then (you guessed it) a *N-N* flux reversal would instantly be
created. Just remember, for each and every reversal in solenoid polarity, a
single flux reversal is created (commit it to memory). An encoded magstripe is
therefore just a series of flux reversals (NN followed by SS followed by NN).
DATA! DATA! DATA! That's what you want! How the hell are flux reversals read
and interpreted as data? Another solenoid called a READ HEAD is used to detect
these flux reversals. The read head operates on the principle of
ELECTROMAGNETIC RECIPROCITY: current passing thru a solenoid produces a
magnetic field at the gap, therefore, the presence of a magnetic field at the
gap of a solenoid coil will *produce a current in the coil*! The strongest
magnetic fields on a magstripe are at the points of flux reversals. These are
detected as voltage peaks by the reader, with +/- voltages corresponding to
NN/SS flux reversals (remember, flux reversals come in 2 flavors).
See Figure 4.
magstripe---> -------NN--------SS--------NN---------SS------
Figure 4: voltage-----> .......+.........-.........+...........-.....
---------
---------- -------------
peak readout--> | | | |
--------| |----------| |----
The "peak readout" square waveform is critical. Notice that the voltage peak
remains the same until a new flux reversal is encountered.
Now, how can we encode DATA? The most common technique used is known as
Aiken Biphase, or "two-frequency coherent-phase encoding" (sounds impressive,
eh?). First, digest the diagrams in Figure 5.
Figure 5: ---------- ---------- ----------
--------- | | | | | | (EH) Control
1 1 1 1 1 ? (FH) End Sentinel
***** 16 Character 5-bit Set *****
10 Numeric Data Characters
3 Framing/Field Characters
3 Control Characters
The magstripe begins with a string of Zero bit-cells to permit the self-
clocking feature of biphase to "sync" and begin decoding. A "Start Sentinel"
character then tells the reformatting process where to start grouping the
decoded bitstream into groups of 5 bits each. At the end of the data, an "End
Sentinel" is encountered, which is followed by an "Longitudinal Redundancy
Check (LRC) character. The LRC is a parity check for the sums of all b1, b2,
b3, and b4 data bits of all preceding characters. The LRC character will catch
the remote error that could occur if an individual character had two
compensating errors in its bit pattern (which would fool the 5th-bit parity
check).
The START SENTINEL, END SENTINEL, and LRC are collectively called "Framing
Characters", and are discarded at the end of the reformatting process.
** ANSI/ISO ALPHA Data Format **
Alphanumeric data can also be encoded on magstripes. The second ANSI/ISO data
format is ALPHA (alphanumeric) and involves a 7-bit character set with 64
characters. As before, an odd parity bit is added to the required 6 data bits
for each of the 64 characters. See Figure 7.
Figure 7:
--------- ANSI/ISO ALPHA Data Format
* Remember that b1 (bit #1) is the LSB (least significant bit)!
* The LSB is read FIRST!
* Hexadecimal conversions of the Data Bits are given in parenthesis (xH).
------Data Bits------- Parity
b1 b2 b3 b4 b5 b6 b7 Character Function
0 0 0 0 0 0 1 space (0H) Special
1 0 0 0 0 0 0 ! (1H) "
0 1 0 0 0 0 0 " (2H) "
1 1 0 0 0 0 1 # (3H) "
0 0 1 0 0 0 0 $ (4H) "
1 0 1 0 0 0 1 % (5H) Start Sentinel
0 1 1 0 0 0 1 & (6H) Special
1 1 1 0 0 0 0 ' (7H) "
0 0 0 1 0 0 0 ( (8H) "
1 0 0 1 0 0 1 ) (9H) "
0 1 0 1 0 0 1 * (AH) "
1 1 0 1 0 0 0 + (BH) "
0 0 1 1 0 0 1 , (CH) "
1 0 1 1 0 0 0 - (DH) "
0 1 1 1 0 0 0 . (EH) "
1 1 1 1 0 0 1 / (FH) "
0 0 0 0 1 0 0 0 (10H) Data (numeric)
1 0 0 0 1 0 1 1 (11H) "
0 1 0 0 1 0 1 2 (12H) "
1 1 0 0 1 0 0 3 (13H) "
0 0 1 0 1 0 1 4 (14H) "
1 0 1 0 1 0 0 5 (15H) "
0 1 1 0 1 0 0 6 (16H) "
1 1 1 0 1 0 1 7 (17H) "
0 0 0 1 1 0 1 8 (18H) "
1 0 0 1 1 0 0 9 (19H) "
0 1 0 1 1 0 0 : (1AH) Special
1 1 0 1 1 0 1 ; (1BH) "
0 0 1 1 1 0 0 < (1CH) "
1 0 1 1 1 0 1 = (1DH) "
0 1 1 1 1 0 1 > (1EH) "
1 1 1 1 1 0 0 ? (1FH) End Sentinel
0 0 0 0 0 1 0 @ (20H) Special
1 0 0 0 0 1 1 A (21H) Data (alpha)
0 1 0 0 0 1 1 B (22H) "
1 1 0 0 0 1 0 C (23H) "
0 0 1 0 0 1 1 D (24H) "
1 0 1 0 0 1 0 E (25H) "
0 1 1 0 0 1 0 F (26H) "
1 1 1 0 0 1 1 G (27H) "
0 0 0 1 0 1 1 H (28H) "
1 0 0 1 0 1 0 I (29H) "
0 1 0 1 0 1 0 J (2AH) "
1 1 0 1 0 1 1 K (2BH) "
0 0 1 1 0 1 0 L (2CH) "
1 0 1 1 0 1 1 M (2DH) "
0 1 1 1 0 1 1 N (2EH) "
1 1 1 1 0 1 0 O (2FH) "
0 0 0 0 1 1 1 P (30H) "
1 0 0 0 1 1 0 Q (31H) "
0 1 0 0 1 1 0 R (32H) "
1 1 0 0 1 1 1 S (33H) "
0 0 1 0 1 1 0 T (34H) "
1 0 1 0 1 1 1 U (35H) "
0 1 1 0 1 1 1 V (36H) "
1 1 1 0 1 1 0 W (37H) "
0 0 0 1 1 1 0 X (38H) "
1 0 0 1 1 1 1 Y (39H) "
0 1 0 1 1 1 1 Z (3AH) "
1 1 0 1 1 1 0 [ (3BH) Special
0 0 1 1 1 1 1 \ (3DH) Special
1 0 1 1 1 1 0 ] (3EH) Special
0 1 1 1 1 1 0 ^ (3FH) Field Separator
1 1 1 1 1 1 1 _ (40H) Special
***** 64 Character 7-bit Set *****
* 43 Alphanumeric Data Characters
* 3 Framing/Field Characters
* 18 Control/Special Characters
The two ANSI/ISO formats, ALPHA and BCD, allow a great variety of data to be
stored on magstripes. Most cards with magstripes use these formats, but
occasionally some do not. More about those later on.
** Tracks and Encoding Protocols **
Now we know how the data is stored. But WHERE is the data stored on the
magstripe? ANSI/ISO standards define *3* Tracks, each of which is used for
different purposes. These Tracks are defined only by their location on the
magstripe, since the magstripe as a whole is magnetically homogeneous. See
Figure 8.
Figure 8:
---------
_________________________________________________________________
| ^ ^ ^
|------------------| 0.223"--|---------|-------------------------
| | | 0.353" | ^
|..................|.........|.........| 0.493" |
| Track #1 0.110" | | |
|............................|.........|...
| | | |
|............................|.........|... |
| Track #2 0.110" | |
|......................................|... |
| | |
|......................................|... |
| Track #3 0.110" |
|.......................................... |
| |
|------------------------------------------------------------------
|
|
|
You can see the exact distances of each track from the edge of the card, as
well as the uniform width and spacing. Place a magstripe card in front of you
with the magstripe visible at the bottom of the card. Data is encoded from
left to right (just like reading a book). See Figure 9.
Figure 9:
--------- ANSI/ISO Track 1,2,3 Standards
Track Name Density Format Characters Function
--------------------------------------------------------------------
1 IATA 210 bpi ALPHA 79 Read Name & Account
2 ABA 75 bpi BCD 40 Read Account
3 THRIFT 210 bpi BCD 107 Read Account &
*Encode* Transaction
*** Track 1 Layout: ***
| SS | FC | PAN | Name | FS | Additional Data | ES | LRC |
SS=Start Sentinel "%"
FC=Format Code
PAN=Primary Acct. # (19 digits max)
FS=Field Separator "^"
Name=26 alphanumeric characters max.
Additional Data=Expiration Date, offset, encrypted PIN, etc.
ES=End Sentinel "?"
LRC=Longitudinal Redundancy Check
*** Track 2 Layout: ***
| SS | PAN | FS | Additional Data | ES | LRC |
SS=Start Sentinel ";"
PAN=Primary Acct. # (19 digits max)
FS=Field Separator "="
Additional Data=Expiration Date, offset, encrypted PIN, etc.
ES=End Sentinel "?"
LRC=Longitudinal Redundancy Check
*** Track 3 Layout: ** Similar to tracks 1 and 2. Almost never used.
Many different data standards used.
Track 2, "American Banking Association," (ABA) is most commonly used. This
is the track that is read by ATMs and credit card checkers. The ABA designed
the specifications of this track and all world banks must abide by it. It
contains the cardholder's account, encrypted PIN, plus other discretionary
data.
Track 1, named after the "International Air Transport Association," contains
the cardholder's name as well as account and other discretionary data. This
track is sometimes used by the airlines when securing reservations with a
credit card; your name just "pops up" on their machine when they swipe your
card!
Since Track 1 can store MUCH more information, credit card companies are trying
to urge retailers to buy card readers that read Track 1. The *problem* is that
most card readers read either Track 1 or Track 2, but NOT BOTH! And the
installed base of readers currently is biased towards Track 2. VISA USA is at
the front of this 'exodus' to Track 1, to the point where they are offering
Track 1 readers at reduced prices thru participating banks. A spokesperson for
VISA commented:
"We think that Track 1 represents more flexibility and the potential
to deliver more information, and we intend to build new services
around the increased information."
What new services? We can only wait and see.
Track 3 is unique. It was intended to have data read and WRITTEN on it.
Cardholders would have account information UPDATED right on the magstripe.
Unfortunately, Track 3 is pretty much an orphaned standard. Its *original*
design was to control off-line ATM transactions, but since ATMs are now on-line
ALL THE TIME, it's pretty much useless. Plus the fact that retailers and banks
would have to install NEW card readers to read that track, and that costs $$.
Encoding protocol specifies that each track must begin and end with a length
of all Zero bits, called CLOCKING BITS. These are used to synch the self-
clocking feature of biphase decoding. See Figure 10.
Figure 10: end sentinel
start sentinel | longitudinal redundancy check
| | |
000000000000000 SS.................ES LRC 0000000000000000
leading data, data, data trailing
clocking bits clocking bits
(length varies) (length varies)
THAT'S IT!!! There you have the ANSI/ISO STANDARDS! Completely explained.
Now, the bad news. NOT EVERY CARD USES IT! Credit cards and ATM cards will
follow these standards. BUT, there are many other types of cards out there.
Security passes, copy machine cards, ID badges, and EACH of them may use a
PROPRIETARY density/format/track-location system. ANSI/ISO is REQUIRED for
financial transaction cards used in the international interbank network. All
other cards can play their own game.
The good news. MOST other cards follow the standards, because it's EASY to
follow a standard instead of WORKING to make your OWN! Most magstripe cards
other than credit cards and ATM cards will use the same Track specifications,
and use either BCD or ALPHA formats.
** A Bit About Magstripe Equipment **
"Wow, now I know how to interpret all that data on magstripes! But.waitasec,
what kind of equipment do I need to read the stripes? Where can I buy a
reader? I don't see any in Radio Shack!!"
Sorry, but magstripe equipment is hard to come by. For obvious reasons, card
readers are not made commonly available to consumers. How to build one is the
topic for another file (this file is already too long).
Your best bets are to try and scope out Electronics Surplus Stores and flea
markets. Do not even bother trying to buy one directly from a manufacturer,
since they will immediately assume you have "criminal motives." And as for
getting your hands on a magstripe ENCODER...well, good luck! Those rare
beauties are worth their weight in gold. Keep your eyes open and look around,
and MAYBE you'll get lucky! A bit of social engineering can go a LONG way.
There are different kinds of magstripe readers/encoders. The most common ones
are "swipe" machines: the type you have to physically slide the card thru.
Others are "insertion" machines: like ATM machines they 'eat' your card, then
regurgitate it after the transaction. Costs are in the thousands of dollars,
but like I said, flea markets and surplus stores will often have GREAT deals
on these things. Another problem is documentation for these machines. If you
call the manufacturer and simply ask for 'em, they will probably deny you the
literature. "Hey son, what are you doing with our model XYZ swipe reader?
That belongs in the hands of a "qualified" merchant or retailer, not some punk
kid trying to "find out how things work!" Again, some social engineering may
be required. Tell 'em you're setting up a new business. Tell 'em you're
working on a science project. Tell 'em anything that works!
2600 Magazine recently had a good article on how to build a machine that copies
magstripe cards. Not much info on the actual data formats and encoding
schemes, but the device described is a start. With some modifications, I bet
you could route the output to a dumb terminal (or thru a null modem cable) in
order to READ the data. Worth checking out the schematics.
As for making your own cards, just paste a length of VCR, reel-to-reel, or
audio cassette tape to a cut-out posterboard or plastic card. Works just as
good as the real thing, and useful to experiment with if you have no expired or
'dead' ATM or calling cards lying around (SAVE them, don't TOSS them!).
** Examples of Data on Magstripes **
The real fun in experimenting with magstripe technology is READING cards to
find out WHAT THE HELL is ON them! Haven't you wondered? The following cards
are the result of my own 'research'. Data such as specific account numbers and
names has been changed to protect the innocent. None the cards used to make
this list were stolen or acquired illegally.
Notice that I make careful note of "common data." This is data that I noticed
was the same for all cards of a particular type. This is highlighted below the
data with asterisks (*). Where I found varying data, I indicate it with "x"'s.
In those cases, NUMBER of CHARACTERS was consistent (the number of "x"'s equals
the number of characters...one to one relationship).
I still don't know what some of the data fields are for, but hopefully I will
be following this file with a sequel after I collect more data. It ISN'T easy
to find lots of cards to examine. Ask your friends, family, and co-workers to
help! "Hey, can I, ahh, like BORROW your MCI calling card tonight? I'm
working on an, ahh, EXPERIMENT. Please?" Just...be honest! Also, do some
trashing. People will often BEND expired cards in half, then throw them out.
Simply bend them back into their normal shape, and they'll usually work (I've
done it!). They may be expired, but they're not ERASED!
-------------------------------------------------------------------------------
-=Mastercard=- Number on front of card -> 1111 2222 3333 4444
Expiration date -> 12/99
Track 2 (BCD,75 bpi)-> ;1111222233334444=99121010000000000000?
***
Track 1 (ALPHA,210 bpi)-> %B1111222233334444^PUBLIC/JOHN?
*
Note that the "101" was common to all MC cards checked, as well as the "B".
-------------------------------------------------------------------------------
-=VISA=- Number on front of card -> 1111 2222 3333 4444
Expiration date -> 12/99
Track 2 (BCD,75 bpi)-> ;1111222233334444=9912101xxxxxxxxxxxxx?
***
Track 1 (ALPHA,210 bpi)-> %B1111222233334444^PUBLIC/JOHN^9912101xxxxxxxxxxxxx?
*
Note that the "101" was common to all VISA cards checked, as well as the "B".
Also, the "xxx" indicates numeric data that varied from card to card, with no
apparent pattern. I believe this is the encrypted pin for use when cardholders
get 'cash advances' from ATMs. In every case, tho, I found *13* digits of the
stuff.
-------------------------------------------------------------------------------
-=Discover=- Number on front of card -> 1111 2222 3333 4444
Expiration date -> 12/99
Track 2 (BCD,75 bpi)-> ;1111222233334444=991210100000?
********
Track 1 (ALPHA,210 bpi)-> %B1111222233334444^PUBLIC/JOHN___^991210100000?
********
Note, the "10100000" and "B" were common to most DISCOVER cards checked. I
found a few that had "10110000" instead. Don't know the significance. Note
the underscores after the name JOHN. I found consistently that the name data
field had *26* characters. Whatever was left of the field after the name was
"padded" with SPACES. So...for all of you with names longer than 25 (exclude
the "/") characters, PREPARE to be TRUNCATED! ;)
-------------------------------------------------------------------------------
-=US Sprint FON=- Number on front of card -> 111 222 3333 4444
Track 2 (BCD,75 bpi)-> ;xxxxxx11122233339==xxx4444xxxxxxxxxx=?
*
Track 1 (ALPHA,210 bpi)-> %B^ /^^xxxxxxxxxxxxxxxxx?
*
Strange. None of the cards I check had names in the Track 1 fields. Track 1
looks unused, yet it was always formatted with field separators. The "xxx"
stuff varied from card to card, and I didn't see a pattern. I know it isn't
a PIN, so it must be account data.
-------------------------------------------------------------------------------
-=Fleet Bank=- Number on front of card -> 111111 222 3333333
Expiration date -> 12/99
Track 2 (BCD,75 bpi)-> ;1111112223333333=9912120100000000xxxx?
****
Track 1 (ALPHA,210 bpi) ->
%B1111112223333333^PUBLIC/JOHN___^9912120100000000000000xxxx000000?
* ****
Note that the "xxx" data varied. This is the encrypted PIN offset. Always 4
digits (hmmm...). The "1201" was always the same. In fact, I tried many ATM
cards from DIFFERENT BANKS...and they all had "1201".
-------------------------------------------------------------------------------
(Can't leave *this* one out ;)
-=Radio Shack=- Number on front of card -> 1111 222 333333
NO EXPIRATION data on card
Track 2 (BCD,75 dpi)-> ;1111222333333=9912101?
*******
Note that the "9912101" was the SAME for EVERY Radio Shack card I saw. Looks
like when they don't have 'real' data to put in the expiration date field, they
have to stick SOMETHING in there.
-------------------------------------------------------------------------------
Well, that's all I'm going to put out right now. As you can see, the major
types of cards (ATMs, CC) all follow the same rules more or less. I checked
out a number of security passcards and timeclock entry cards..and they ALL had
random stuff written to Track 2. Track 2 is by FAR the MOST utilized track on
the card. And the format is pretty much always ANSI/ISO BCD. I *did* run into
some hotel room access cards that, when scanned, were GARBLED. They most
likely used a character set other than ASCII (if they were audio tones, my
reader would have put out NOTHING...as opposed to GARBLED data). As you can
see, one could write a BOOK listing different types of card data. I intended
only to give you some examples. My research has been limited, but I tried to
make logical conclusions based on the data I received.
** Cards of All Flavors **
People wanted to store A LOT of data on plastic cards. And they wanted that
data to be 'invisible' to cardholders. Here are the different card
technologies that were invented and are available today.
HOLLERITH - With this system, holes are punched in a plastic or paper card and
read optically. One of the earliest technologies, it is now seen
as an encoded room key in hotels. The technology is not secure,
but cards are cheap to make.
BAR CODE - The use of bar codes is limited. They are cheap, but there is
virtually no security and the bar code strip can be easily damaged.
INFRARED - Not in widespread use, cards are factory encoded by creating a
"shadow pattern" within the card. The card is passed thru a swipe
or insertion reader that uses an infrared scanner. Infrared card
pricing is moderate to expensive, and encoding is pretty secure.
Infrared scanners are optical and therefore vulnerable to
contamination.
PROXIMITY - Hands-free operation is the primary selling point of this card.
Although several different circuit designs are used, all proximity
cards permit the transmission of a code simply by bringing the card
near the reader (6-12"). These cards are quite thick, up to
0.15" (the ABA standard is 0.030"!).
WIEGAND - Named after its inventor, this technology uses a series of small
diameter wires that, when subjected to a changing magnetic field,
induce a discrete voltage output in a sensing coil. Two rows of
wires are embedded in a coded strip. When the wires move past
the read head, a series of pulses is read and interpreted as binary
code. This technology produces cards that are VERY hard to copy
or alter, and cards are moderately expensive to make. Readers
based on this tech are epoxy filled, making them immune to weather
conditions, and neither card nor readers are affected by external
magnetic fields (don't worry about leaving these cards on top of
the television set...you can't hurt them!). Here's an example of
the layout of the wires in a Wiegand strip:
||| || || | ||| | || || | || || | | ||
| | | | | | |||| || |||| ||
The wires are NOT visible from the outside of the card, but if
your card is white, place it in front of a VERY bright light source
and peer inside. Notice that the spacings between the wires is
uniform.
BARIUM FERRITE - The oldest magnetic encoding technology (been around for 40
yrs!) it uses small bits of magnetized barium ferrite that are
placed inside a plastic card. The polarity and location of
the "spots" determines the coding. These cards have a short
life cycle, and are used EXTENSIVELY in parking lots (high
turnover rate, minimal security). Barium Ferrite cards are
ONLY used with INSERTION readers.
There you have the most commonly used cards. Magstripes are common because
they are CHEAP and relatively secure.
** Magstripe Coercivity **
Magstripes themselves come in different flavors. The COERCIVITY of the
magnetic media must be specified. The coercivity is the magnetic field
strength required to demagnetize an encoded stripe, and therefore determines
the encode head field strength required to encode the stripe. A range of media
coercivities are available ranging from 300 Oersteds to 4,000 Oe. That boils
down to HIGH-ENERGY magstripes (4,000 Oe) and LOW-ENERGY magstripes (300 Oe).
REMEMBER: since all magstripes have the same magnetic remanence regardless of
their coercivity, readers CANNOT tell the difference between HIGH and LOW
energy stripes. Both are read the same by the same machines.
LOW-ENERGY media is most common. It is used on all financial cards, but its
disadvantage is that it is subject to accidental demagnetization from contact
with common magnets (refrigerator, TV magnetic fields, etc.). But these cards
are kept safe in wallets and purses most of the time.
HIGH-ENERGY media is used for ID Badges and access control cards, which are
commonly used in 'hostile' environments (worn on uniform, used in stockrooms).
Normal magnets will not affect these cards, and low-energy encoders cannot
write to them.
** Not All that Fluxes is Digital **
Not all magstripe cards operate on a digital encoding method. SOME cards
encode AUDIO TONES, as opposed to digital data. These cards are usually
used with old, outdated, industrial-strength equipment where security is not an
issue and not a great deal of data need be encoded on the card. Some subway
passes are like this. They require only expiration data on the magstripe, and
a short series of varying frequencies and durations are enough. Frequencies
will vary with the speed of swiping, but RELATIVE frequencies will remain the
same (for instance, tone 1 is twice the freq. of tone 2, and .5 the freq of
tone 3, regardless of the original frequencies!). Grab an oscilloscope to
visualize the tones, and listen to them on your stereo. I haven't experimented
with these types of cards at all.
** Security and Smartcards **
Many security systems utilize magstripe cards, in the form of passcards and ID
cards. It's interesting, but I found in a NUMBER of cases that there was a
serious FLAW in the security of the system. In these cases, there was a code
number PRINTED on the card. When scanned, I found this number encoded on the
magstripe. Problem was, the CODE NUMBER was ALL I found on the magstripe!
Meaning, by just looking at the face of the card, I immediately knew exactly
what was encoded on it. Ooops! Makes it pretty damn easy to just glance at
Joe's card during lunch, then go home and pop out my OWN copy of Joe's access
card! Fortunately, I found this flaw only in 'smaller' companies (sometimes
even universities). Bigger companies seem to know better, and DON'T print
ALL of the magstripe data right on card in big, easily legible numbers. At
least the big companies *I* checked. ;)
Other security blunders include passcard magstripes encoded ONLY with the
owner's social security number (yeah, real difficult to find out a person's
SS#...GREAT idea), and having passcards with only 3 or 4 digit codes.
Smartcard technology involves the use of chips embedded in plastic cards, with
pinouts that temporarily contact the card reader equipment. Obviously, a GREAT
deal of data could be stored in this way, and unauthorized duplication would be
very difficulty. Interestingly enough, not much effort is being put into
smartcards by the major credit card companies. They feel that the tech is too
expensive, and that still more data can be squeezed onto magstripe cards in the
future (especially Track 1). I find this somewhat analogous to the use of
metallic oxide disk media. Sure, it's not the greatest (compared to erasable-
writable optical disks), but it's CHEAP..and we just keep improving it.
Magstripes will be around for a long time to come. The media will be refined,
and data density increased. But for conventional applications, the vast
storage capabilities of smartcards are just not needed.
** Biometrics: Throw yer cards away! **
I'd like to end with a mention of biometrics: the technology based on reading
the physical attributes of an individual thru retina scanning, signature
verification, voice verification, and other means. This was once limited to
government use and to supersensitive installations. However, biometrics will
soon acquire a larger market share in access control sales because much of its
development stage has passed and costs will be within reach of more buyers.
Eventually, we can expect biometrics to replace pretty much ALL cards..because
all those plastic cards in your wallet are there JUST to help COMPANIES
*identify* YOU. And with biometrics, they'll know you without having to read
cards.
I'm not paranoid, nor do I subscribe to any grand "corporate conspiracy," but I
find it a bit unsettling that our physical attributes will most likely someday
be sitting in the cool, vast electronic databases of the CORPORATE world.
Accessible by anyone willing to pay. Imagine CBI and TRW databases with your
retina image, fingerprint, and voice pattern online for instant, convenient
retrieval. Today, a person can CHOOSE NOT to own a credit card or a bank
card...we can cut up our plastic ID cards! Without a card, a card reader is
useless and cannot identify you.
Paying in cash makes you invisible! However, with biometrics, all a machine
has to do is watch... listen...and record. With government/corporate America
pushing all the buttons. "Are you paying in cash?..Thank you...Please look
into the camera. Oh, I see your name is Mr. Smith...uh, oh...my computer tells
me you haven't paid your gas bill...afraid I'm going to have to keep this money
and credit your gas account with it....do you have any more cash?...or would
you rather I garnish your paycheck?" heh heh
** Closing Notes (FINALLY!!!!) **
Whew...this was one MOTHER of a file. I hope it was interesting, and I hope
you distribute it to all you friends. This file was a production of
"Restricted Data Transmissions"...a group of techies based in the Boston area
that feel that "Information is Power"...and we intend to release a number of
highly technical yet entertaining files in the coming year....LOOK FOR THEM!!
Tomorrow I'm on my way to Xmascon '91... we made some slick buttons
commemorating the event...if you ever see one of them (green wreath.XMASCON
1991 printed on it).hang on to it!... it's a collector's item.. (hahahah)
Boy, I'm sleepy...
Remember.... "Truth is cheap, but information costs!"
But -=RDT is gonna change all that... ;) set the info FREE!
Peace.
..oooOO Count Zero OOooo..
Usual greets to Magic Man, Brian Oblivion, Omega, White Knight, and anyone
else I ever bummed a cigarette off.
(1/18/92 addition: Greets to everyone I met at Xmascon..including but not
excluding Crimson Death, Dispater, Sterling, Mack Hammer, Erik Bloodaxe,
Holistic Hacker, Pain Hertz, Swamp Ratte, G.A.Ellsworth, Phaedrus, Moebius,
Lord MacDuff, Judge Dredd, and of course hats off to *Drunkfux* for organizing
and taking responsibility for the whole damn thing. Hope to see all of you
at SummerCon '92! Look for Cyber-striper GIFs at a BBS near you..heh heh)
Comments, criticisms, and discussions about this file are welcome. I can be
reached at:
count0@world.std.com
count0@spica.bu.edu
count0@atdt.org
Magic Man and I are the sysops of the BBS "ATDT"...located somewhere in
Massachusetts. Great message bases, technical discussions...data made
flesh...electronic underground.....our own Internet address (atdt.org)...
field trips to the tunnels under MIT in Cambridge.....give it a call..
mail me for more info.. ;)